After a mobile part is switched on, it starts searching for a base station. When a suitable base station is found, the mobile station synchronizes to the base station in order to establish and maintain a connection. For supporting the mobile station to lock on, a base station is continuously transmitting information on its identity and synchronization information on at least one channel.
In a DECT system, a base station broadcasts such information via a dummy bearer or beacon. In the following, the terms “dummy bearer” and “beacon” will be used synonymously. A dummy bearer usually comprises information about the identity of the base station, synchronization information, paging information and the like. In an unlocked state, a mobile station scans the relevant DECT channels to find a dummy bearer transmitted by a base station. Once a dummy bearer of a preferred base station is found, the mobile station will synchronize its timing with the timing of the base station and keep listening to further information broadcasted by the base station. The mobile station is now locked to the base station.
The DECT standard is provided by the European Telecommunications Standards Institute (ETSI). A current version of the DECT standard may, for example, be accessed by the home page of the ETSI (www.etsi.org). All contents of the DECT standard are incorporated herewith by reference.
According to the DECT standard, a mobile station does not receive information from the base station about frequency channels the base station will use for broadcasting its dummy bearer. That is, only after the mobile station has synchronized to the base station, the mobile station knows which channel is actually used. Information about a change of the dummy bearer channel is only broadcasted in certain frames. The mobile station can therefore only know the actual dummy bearer channel and in case of a change of the dummy bearer channel by staying in synchronization and constantly monitor the dummy bearer. If synchronization is lost, the mobile station is thus forced to scan the DECT channels one after another until a proper dummy bearer is found. An extended time required for searching a dummy bearer results in an increased energy consumption of the mobile station, since the mobile stations' radio receiver has to be active during the searching procedure. The increased energy consumption in turn leads to a reduced life time of the mobile stations' battery or accumulator.